Stock-Based Compensation - Summary of RSU Activity (Detail) - Restricted Stock Units (RSUs) [Member] - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Number of shares subject to restriction, Beginning Balance	422,263
Number of shares subject to restriction, Granted	449,495
Number of shares subject to restriction, Vested	(4,044)
Number of shares subject to restriction, Forfeited	(65,012)
Number of shares subject to restriction, Ending Balance	802,702	422,263
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted average share value, Beginning Balance	$ 28.43
Weighted average share value, Granted	27.16
Weighted average share value, Vested	28.44
Weighted average share value, Forfeited	27.32
Weighted average share value, Ending Balance	$ 27.81	$ 28.43
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Weighted average remaining contractual term, Beginning Balance	2 years 7 days	2 years 7 months 13 days
Weighted average remaining contractual term, Ending Balance	2 years 7 days	2 years 7 months 13 days
Aggregate intrinsic value, Beginning Balance	$ 11,756
Aggregate intrinsic value, Ending Balance	$ 27,019	$ 11,756